Environmental Science Chapter 7: Population Characteristics

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Questions and Answers

What is a population in the context of environmental science?

A group of individuals of the same gender

A group of individuals of the same species inhabiting the same area (correct)

A group of different species inhabiting the same area

A group of individuals of the same age

What is natality in the context of population characteristics?

The number of individuals emigrating from an area

The number of individuals migrating to a new area

The number of individuals added to a population through reproduction over a particular time period (correct)

The number of deaths in a population over a particular time period

What is mortality in the context of population characteristics?

The number of individuals migrating to a new area

The number of individuals emigrating from an area

The number of deaths in a population over a particular time period (correct)

The number of individuals added to a population through reproduction over a particular time period

What does a survivorship curve show?

The proportion of individuals likely to survive to each age Signup and view all the answers

How many types of survivorship curves can be recognized?

Three Signup and view all the answers

What is the unit of measurement for birth rate and death rate?

Per 1,000 individuals per year Signup and view all the answers

What is the approximate combined population of more-developed countries?

1.27 billion Signup and view all the answers

What is the expected growth rate of more-developed countries between 2020 and 2050?

3.5% Signup and view all the answers

What is the approximate number of people living on less than $1.90 per day?

700 million Signup and view all the answers

What is the key factor that contributes to environmental problems?

Human population growth Signup and view all the answers

What is the ecological footprint of a population?

The land area required to provide resources and absorb wastes Signup and view all the answers

What is the study of populations and their characteristics known as?

Demography Signup and view all the answers

What is the result of a high birth rate and low death rate?

High population growth Signup and view all the answers

What is the total fertility rate that is known as replacement fertility?

2.1 Signup and view all the answers

What is the major social factor determining family size?

Status and desires of women in the culture Signup and view all the answers

What is the result of early marriages?

High fertility rates Signup and view all the answers

What is the population growth rate in human population studies?

Birthrate minus death rate Signup and view all the answers

What does the sex ratio refer to in a population?

Relative number of males and females Signup and view all the answers

What is the effect of high population density on individuals in a population?

They compete severely for resources Signup and view all the answers

What is biotic potential?

The inherent reproductive capacity of a species Signup and view all the answers

What is the stable equilibrium phase of population growth?

The phase where the death rate and birth rate are equal Signup and view all the answers

What is environmental resistance?

The collective limiting factors that act on a population Signup and view all the answers

What type of limiting factor becomes more effective as the density of the population increases?

Density-dependent limiting factor Signup and view all the answers

What is carrying capacity?

The maximum sustainable population for an area Signup and view all the answers

What can influence the carrying capacity of an area?

Several factors including successional changes, climate variations, and disease epidemics Signup and view all the answers

What is dispersal in the context of population ecology?

The movement of individuals from densely populated locations to new areas Signup and view all the answers

What is the projected human population by 2050 if the current growth rate of 1.1% continues?

nearly 10 billion Signup and view all the answers

What is a common feature of population growth curves?

A lag phase followed by an exponential growth phase, a deceleration phase, and a stable equilibrium phase Signup and view all the answers

What is the primary factor that determines population growth rates?

Both biological and social and economic factors Signup and view all the answers

What is the demographic transition model suggesting?

That population growth rates stabilize as a country becomes industrialized Signup and view all the answers

Where is most of the population growth occurring?

Less-developed countries Signup and view all the answers

What is a common reason why people from less-developed countries migrate to developed countries?

To seek a higher standard of living Signup and view all the answers

What is the study of human populations and the things that affect them?

Demography Signup and view all the answers

What is an important economic measure of standard of living?

Gross national income (GNI) Signup and view all the answers

Why do people in less-developed countries feed at lower trophic levels?

Because they must eat plants themselves instead of feeding the plants to animals and eating the animals Signup and view all the answers

What is a consequence of over-nutrition in more-developed countries?

Obesity Signup and view all the answers

What is a challenge in solving the problem of food distribution?

Providing temporary relief of symptoms Signup and view all the answers

What is the demographic transition model based on?

The historical, social, and economic development of Europe and North America Signup and view all the answers

What happens to the birth rate and death rate in the final stage of the demographic transition model?

The birth rate and death rate become equal Signup and view all the answers

What contributed to the population growth trends in the United States?

All of the above Signup and view all the answers

What is a consequence of a lack of protein in the diet?

Malnutrition Signup and view all the answers

What is a factor that determines food availability in less-developed countries?

War, repayment of foreign debt, corruption, and poor management Signup and view all the answers

What is the primary characteristic of a K-strategist?

Provides substantial parental care Signup and view all the answers

What type of limiting factors control r-strategist populations?

Density-independent Signup and view all the answers

Which of the following is NOT a characteristic of an r-strategist?

Provides substantial parental care Signup and view all the answers

What is the current trend in human population growth?

Increasing rapidly Signup and view all the answers

What is the approximate doubling time for the human population?

35 years Signup and view all the answers

What type of population growth pattern do K-strategists exhibit?

Exponential growth followed by a stable equilibrium stage Signup and view all the answers

Which of the following is an example of an r-strategist?

Protozoa Signup and view all the answers

What is the main reason for the increasing human population growth?

Lowering of the death rate due to control of disease and improved food production Signup and view all the answers

What is the typical environment occupied by K-strategists?

Stable environments Signup and view all the answers

What is the predicted human population size in 2043?

9 billion Signup and view all the answers

Why do breast-feeding women have a lower likelihood of pregnancy?

Because breast-feeding suppresses ovulation Signup and view all the answers

What is a social factor that influences population growth rates?

Lack of education opportunities for women Signup and view all the answers

In which countries do children contribute to the family economy?

Less developed countries Signup and view all the answers

What is a policy implemented by some European countries to encourage higher fertility rates?

Paid maternity leave Signup and view all the answers

What is a characteristic of the population in countries with high infant mortality rates?

High fertility rates Signup and view all the answers

What is a consequence of large families in developed countries?

They are an economic drain Signup and view all the answers

What is a political factor that influences population growth rates?

Government policies to encourage or limit fertility rates Signup and view all the answers

Why do some countries have immigration policies that encourage immigration?

To offset a potential decline in the number of working-age citizens Signup and view all the answers

What is a trend observed in countries with low fertility rates?

Decreasing population growth rates Signup and view all the answers

What is a characteristic of the population in Nigeria?

High fertility rate and high infant mortality rate Signup and view all the answers

Study Notes

Population Characteristics

A population is a group of individuals of the same species inhabiting the same area.
Genetic differences commonly exist within different populations of a given species.
Natality: The number of individuals added to a population through reproduction over a particular time period.
Birth Rate = Humans born per 1,000 individuals per year.
Mortality: The number of deaths in a population over a particular time period.
Death Rate = Human deaths per 1,000 individuals per year.

Survivorship Curves

A survivorship curve shows the proportion of individuals likely to survive to each age.
Three types of survivorship curves can be recognized:
- Species with high mortality in young.
- Species with mortality equitable among age classes.
- Species with mortality high only in old age.

Population Growth Rate

Population growth rate is the birth rate minus the death rate.
In human population studies, it is often expressed as a percentage of the total population.
Sex ratio refers to the relative number of males and females in a population.
The number of females is important because females determine the number of offspring produced in sexually reproducing populations.
Age distribution is the number of individuals of each age in the population.
Age distribution greatly influences the population growth rate.

Population Density and Spatial Distribution

Population density is the number of individuals per unit area.
High population density injures all individuals within the population because they compete severely for necessary resources.
Dispersal: Movement of individuals from densely populated locations to new areas.
Emigration: Movement from an area.
Immigration: Movement into an area.

Population Growth Curve

Biotic potential is the inherent reproductive capacity of a species (biological ability to produce offspring).
Population growth follows a pattern consisting of:
- Lag phase: Slow population growth.
- Exponential growth phase (Log phase): More organisms are reproducing, causing accelerated growth.
- Deceleration phase: The population growth rate slows as the death rate and birth rate come to equal one another.
- Stable equilibrium phase: The death rate and birth rate become equal, and the population stops growing.

Factors That Limit Population Size

Factors that prevent unlimited population growth are known as limiting factors.
All of the different limiting factors that act on a population are collectively known as environmental resistance.
Extrinsic limiting factors are those that come from outside the population.
Intrinsic limiting factors are those factors that originate within the population and exercise control over it.
Density-dependent limiting factors are those that become more effective as the density of the population increases.
Density-independent limiting factors are population-controlling influences that are not related to the density of the population.

Categories of Limiting Factors

Four main categories of limiting factors:
- Raw material availability.
- Energy availability.
- Accumulation of waste products.
- Interactions among organisms.

Carrying Capacity

Carrying capacity is the maximum sustainable population for an area.
It is not an inflexible number; it can be influenced by environmental differences such as:
- Successional changes.
- Climate variations.
- Disease epidemics.
- Forest fires, floods, or natural disasters.
- Nutrient levels in aquatic ecosystems.

Reproductive Strategies and Population Fluctuations

Species can be divided into two broad categories based on their reproductive strategies:
- K-strategists: Organisms that typically reach a stable population as the population reaches the carrying capacity.
- r-strategists: Typically, these are small organisms that have a short life, produce many offspring, exploit unstable environments, and do not reach a carrying capacity.

Human Population Growth

The human population has been increasing rapidly.
A major reason for the increasing human population growth is a lowering of the death rate due to control of disease and improved food production.
The doubling time for the human population is calculated by: 70 / annual rate of increase (%).

Human Population Characteristics and Implications

The world can be divided into two segments based on economic development:
- More-developed countries (MDCs): Europe, Canada, the U.S., Japan, Australia, and New Zealand.
- Less-developed countries (LDCs): All other remaining countries of the world.
Human population growth is tied to economic development and is a contributing factor to nearly all environmental problems.
Population density relates the size of the population to available resources.
Affluence and technology are important contributors to environmental impact.

Factors That Influence Human Population Growth

Biological factors:
- Demography is the study of populations and their characteristics, how those characteristics affect growth, and the consequences of that growth.
- The balance between the birth rate and death rate has a large influence on population growth.
- The age distribution of a population influences population growth.
- Zero population growth is when the birth rate equals the death rate.
- The total fertility rate of a population is the number of children a woman has during her lifetime.
Social factors:
- Reducing fertility rates would be advantageous, especially in LDCs, but not everyone agrees.
- Several factors (religious, traditional, social, and economic) influence the number of children a couple would like to have.
- The major social factors determining family size are the status and desires of women in the culture.
- Early marriages foster high fertility rates.
- Women are exposed to a high likelihood of pregnancy for longer.
- Childrearing practices also influence population growth rates.
- Breastfeeding is an important factor in population growth.
- Lack of education opportunities for women reduces their options.
- Financial independence leads to marriage later in life.
- Better-educated women are more likely to have access to and use birth control.
- In some cultures, women desire large families.
Economic factors:
- In LDCs, the economic benefits of children are extremely important.
- Even young children can be given jobs that contribute to the family economy.
- In the developed world, large numbers of children are an economic drain.
- They are prevented from working.
- They must be sent to school at great expense.
- They consume large amounts of the family income.
Political factors:
- Governments can either reward or punish high fertility rates.
- Several European countries are concerned about low birth rates and have instituted policies to encourage couples to have more children.
- Paid maternity leave and guaranteed job availability upon the mother's return to work.
- Childcare facilities make it possible for both parents to work.
- Child tax deductions provide an indirect payment to families.

Population Growth Rates and Standard of Living

There appears to be an inverse relationship between a country's growth rate and its average standard of living.
Standard of living is a difficult concept to quantify since various cultures have different desires.
Factors usually included in an analysis of standard of living:
- Economic well-being.
- Health conditions.
- Social status and mobility.
- An important economic measure of standard of living is the average purchasing power per person.
- Gross national income (GNI) is an index of purchasing power measuring total goods and services generated by citizens of a country.

Hunger, Food Production, and Environmental Degradation

People in LDCs generally feed at lower trophic levels than those in the developed world.
A lack of protein in the diet can lead to malnutrition.
Many people in more-developed countries suffer from over-nutrition.
About 66% of North Americans are overweight or obese.
In countries where food is in short supply, agricultural land is already being exploited to its limit, and there is still a need for more food.
Many more-developed countries are net food exporters.
Improved plant varieties and agricultural techniques have dramatically increased food production in some parts of the world.
Political activities such as war, repayment of foreign debt, corruption, and poor management often determine food availability.

The Demographic Transition Concept

Demographic transition is a model that describes changes in population growth rates based on the historical, social, and economic development of Europe and North America.
Initially, countries have a stable population with high birth and death rates.
Improvements in food production, and healthier living conditions cause the death rate to fall while the birth rate remains high, and the population grows.### Population Growth and Demographic Transition
As technological development and economic well-being improve, birth rates fall, eventually stabilizing the population with low birth rates and low death rates.